test(api)+docs: assert matchedRemittance=null; fail-loud on fixture drift; tighten docstring

backend/src/cyclone/api.py

@@ -714,20 +714,16 @@ def list_claims(
 
 @app.get("/api/claims/{claim_id}")
 def get_claim_detail_endpoint(claim_id: str) -> dict:
-    """Return one claim with full drawer context.
+    """Return one claim with full drawer context (SP4).
 
-    SP4 detail-drawer endpoint. The body is the spec-shaped dict
-    produced by :meth:`CycloneStore.get_claim_detail` — header, state,
-    service lines, diagnoses, parties, validation, raw segments,
-    ``stateHistory`` (most-recent-first, capped at 50), and a
-    populated ``matchedRemittance`` block if the claim is paired.
+    Body shape is produced by :meth:`CycloneStore.get_claim_detail`:
+    header, state, service lines, diagnoses, parties, validation,
+    raw segments, ``stateHistory`` (most-recent-first, capped at 50),
+    and a populated ``matchedRemittance`` block when paired.
 
-    Path param is ``claim_id`` (not ``id``) to avoid shadowing
-    FastAPI's internal ``id`` name and to keep OpenAPI docs self-
-    describing (matches the ``/api/acks/{ack_id}`` convention from
-    SP3). Returns 404 when the claim is missing — never 500 — so the
-    UI can distinguish "claim doesn't exist" from a transient fetch
-    failure.
+    Path param is ``claim_id`` (matches the SP3 ``/api/acks/{ack_id}``
+    convention). Returns 404 — never 500 — on a missing claim so the
+    UI can distinguish "doesn't exist" from a transient fetch error.
     """
     body = store.get_claim_detail(claim_id)
     if body is None:

backend/tests/test_api_claim_detail.py

@@ -103,6 +103,11 @@ def test_get_claim_detail_happy_path(seeded_store):
         "validation", "rawSegments", "matchedRemittance", "stateHistory",
     ):
         assert k in body, f"missing key {k!r}"
+    # Spec §3.2: matchedRemittance is `null` for an unpaired claim
+    # (the dominant UI render path). The matched-populated case is
+    # covered separately in
+    # test_get_claim_detail_matched_remit_inlines_summary.
+    assert body["matchedRemittance"] is None
     assert body["id"] == cid
     # billedAmount is a number (not a Decimal string).
     assert isinstance(body["billedAmount"], (int, float))
@@ -140,7 +145,11 @@ def test_get_claim_detail_state_history_includes_manual_match(seeded_store_with_
         "/api/reconciliation/unmatched", headers=JSON,
     ).json()
     if not unmatched["claims"] or not unmatched["remittances"]:
-        pytest.skip("seeded fixtures don't produce an unmatched pair")
+        pytest.fail(
+            "co_medicaid_837p.txt + co_medicaid_835.txt fixtures no longer "
+            "produce an unmatched pair; matched-remit tests need updating "
+            "(see seeded_store_with_pair docstring for the expected invariant)"
+        )
     claim_id = unmatched["claims"][0]["id"]
     remit_id = unmatched["remittances"][0]["id"]
 
@@ -180,7 +189,11 @@ def test_get_claim_detail_matched_remit_inlines_summary(seeded_store_with_pair):
         "/api/reconciliation/unmatched", headers=JSON,
     ).json()
     if not unmatched["claims"] or not unmatched["remittances"]:
-        pytest.skip("seeded fixtures don't produce an unmatched pair")
+        pytest.fail(
+            "co_medicaid_837p.txt + co_medicaid_835.txt fixtures no longer "
+            "produce an unmatched pair; matched-remit tests need updating "
+            "(see seeded_store_with_pair docstring for the expected invariant)"
+        )
     claim_id = unmatched["claims"][0]["id"]
     remit_id = unmatched["remittances"][0]["id"]
     seeded_store_with_pair.post(